[clang] Fix scope of typedefs present inside a template class (PR #146729)

[David Blaikie via cfe-commits]

================
@@ -4189,8 +4189,13 @@ llvm::DICompositeType *CGDebugInfo::CreateLimitedType(const RecordType *Ty) {
         llvm::MDNode::replaceWithDistinct(llvm::TempDICompositeType(RealDecl));
     break;
   }
-
-  RegionMap[Ty->getDecl()].reset(RealDecl);
+  if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(Ty->getDecl())) {
+    CXXRecordDecl *TemplateDecl =
+        CTSD->getSpecializedTemplate()->getTemplatedDecl();
+    RegionMap[TemplateDecl].reset(RealDecl);
+  } else {
+    RegionMap[Ty->getDecl()].reset(RealDecl);
+  }
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dwblaikie wrote:

But I'm still a bit confused by this code in general - the `templated decl` is the generic thing, right? But DWARF doesn't describe generic things, so we'd want to put these nested elements in specific instantiations... 

(presumably if this patch is the right path forward, we'd need something similar for the `RegionMap.erase(Ty->getDecl());` ? (or perhapps that's matched up with some other mutation))

https://github.com/llvm/llvm-project/pull/146729